DE1913901A1 - Cold light mirror - Google Patents

Description

BALZERS PATENT- UND BLiTEILISUSGO AKTIENGESELLSCHAFT, FL - 9496 Balzers, Principality of Liechtenstein

BALZERS + PFEIFFER HOCHVAKUUM GMBH Heinrich-Hertz-Str. 6th D - 6 Frankfurt / M. 9o

Cold light mirror

The present invention relates to cold mirrors such as aie in particular by vapor deposition of thin layers documents and, for example, cinema projectors are used to separate heat radiation from visible light.

A cold-light mirror is known, with a carrier permeable to heat rays and vapor-deposited thin surface layers, the lowest, mainly reflective, layer consisting of the purest silicon and covered by several layers of dielectric vapor vapor-deposited thereon made of alternately higher and lower refractive index substances. This known cold light mirror has z, L. On top of the silicon layer there are 4 to 6 layers of alternating silicon oxide and titanium oxide or tantulin oxide, with the silicon layer being preceded by a layer of silicon oxide. This well-known proposal assumes that the purest silicon of

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the limit of the visible spectrum is permeable to heat rays and in the visible reflects a substantial part of the radiation. With a suitable layer thickness, a reflection of approx. 62% for visible light is achieved; such a mirror would be very uneconomical; around. To arrive at a reflection coefficient of over 90 / », which only results in an economic benefit, one could think of increasing the reflection to the stated value by a series of interfering icks on the surface of the silicon mirror. However, even if, for example, 4 additional layers of alternating oxides of 'x'itan and silicon are vapor-deposited, you only achieve a reflection of around $ 75, with 6 additional layers of around 80? » in the hit te of the reflected 3-spectral range. Experience has shown that for a cold-light mirror manufactured according to the known proposal from a basic layer by oilizLum and additional layers, significantly more additional layers are required if one wants to achieve a clean, color-cast-free separation of the spectral range to be transmitted from the 3-spectral range to be reflected.

According to the original invention, a layer structure is proposed which Surprisingly, this problem can be solved with significantly fewer reports. It. it was found to be more beneficial is not just a silicon layer as a reflective base layer to use which one i'iehrschichtsystera from others alternating high and low breaking otoffen follows, but several oiliziunischichben as high-refractive sub-layers to use a multilayer interference system.

The invention accordingly relates to a cold light mirror which has a silicon layer on a carrier permeable to heat radiation and then further alternating high and low refractive alternating layers of approximately λ / 4 optical thickness of the middle one wavelength λ - 55Onut of the visible spectral range on

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are brought and is characterized in that on the Following the first silicon layer, at least one further silicon layer separated from the first by a lower refractive index layer is upset.

A tried and tested embodiment of the invention is a cold light mirror which has 5 layers applied to a heat-radiation-permeable layer, the first layer made of silicon on the carrier, the following layer made of silicon oxide, preferably SiCp, and the third layer again made of silicon consists, the thickness. each of the layers is equal to λ / 4 of the wavelength λ = 550 incudes of the visible upectral range. To increase the effect, a layer of λ / 4 optical thickness made of 3iC _? and TiC applied. .Oasi + air · achieves a reflection of over 90 .- 'j in the middle of the reflected spectral range, that is, a few times more than is achieved in the above-mentioned examples according to the sunlit method of technology with the same number or even more layers. The resistance of multi-layer systems built up according to the invention is excellent. Sodium salt water (Jm or'ifen to the Bestrindi-lity, the above-mentioned cold mirror in yj was) determined. It was found that after 100 hours no erosion of any kind was noticeable.

Instead of the low-refractive layer substance, for example All other known substances that have been tried and tested for low-refraction layers, such as e.g. magnesium fluoride, can also be used step. With magnesium fluoride it was possible with otherwise the same structure of the 5-layer system, as in the example mentioned above, a reflection that is approx. 2 to 3% higher can be achieved. The durability such a layer system against moisture and mechanical Abrasion was also excellent. According to the invention Iyiehrschichtsysteme also have a very good thermal shock resistance shown.

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In the attached drawing are two examples of a light mirror shown schematically according to the invention.

-Fig. 1 shows a section of a concave mirror on which Inside according to the example described above 5 »layers in in the order silicon, silicon oxide, silicon, silicon oxide, Titanium oxide are applied. 1 denotes the one that is permeable to heat radiation opaque body e.g. made of oil, 2 the silicon layers, 3 the silicon oxide layers and 4 the titanium oxide layer.

iig. 2 shows a similar one as the i> tuck of a plane mirror ■ Jchichtsyatem where 5 the silicon layers, 6 the magnesium fluoride - and 7 means a titanium oxide layer.

The uchichtdieken are not drawn massatäblicrx and are in both examples λ / 4 (optical layer thickness!) Of the desired center of gravity wavelength.

PH 6849

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Claims (2)

PiTEBTAUäPRÜBOHB (IJ cold-light mirror, in which on a heat-radiation-permeable Carrier a silicon layer and then further alternating high and low refractive index layers, for example of .λ / 4 optical thickness of the mean wave length Λ = 55o m ^ of the visible spectral range are applied, characterized in that on the first Following the silicon layer, at least one further silicon layer separated from the first by a low refractive index layer is upset. 2. Cold light mirror according to claim 1, characterized in that the in the order The specified layers consist of silicon, silicon oxide, silicon, silicon oxide, titanium oxide. 3 · cold light mirror according to claim 1, characterized in that the specified in the Sequence of layers of silicon, magnesium fluoride, silicon, magnesium fluoride and titanium oxide applied to the carrier exist. PR 6849 009816/1175 Blank page